This invention relates to dredging systems in general and more particularly to improved equipment for removal of material from the bottom of a body of water.
Dredging apparatus often includes a boom or ladder pivotally suspended from a floating vessel to guide underwater movement of an excavating head along a bottom surface. According to one type of dredging system, the excavating head is in the form of a drum rotated in one direction to pick up mud, sand, gravel or other material. The excavated material is collected within the drum and removed therefrom by suction pressure through a conveying conduit extending up the ladder to the floating vessel for discharge. Dredging systems of the foregoing type are disclosed, for example, in U.S. Pat. Nos. 362,796, 903,210, 3,476,498 and 3,614,837.
Travel of the excavating head along the bottom surface is confined to an arcuate path about an anchoring spud according to each of the foregoing patents. Also, according to U.S. Pat. No. 363,685 to Bostrom, the drum is formed by two conical sections extending axially from a central suction manifold to which the material conveying conduit is connected. According to U.S. Pat. Nos. 903,210, 3,476,497 and 3,614,837, scooping elements project from the drum to displace the excavated material into partitioned collecting spaces within the drum. The drum in each case is supported for rotation about an axis fixed to the lower end of the boom or ladder.
Excavating heads that are not confined to arcuate travel during operation, are also known. U.S. Pat. No. 3,919,790 to Sasaki et al discloses, for example, an underwater traveling frame pivotally connected to the lower end of a towing boom. The frame rotatably mounts a bucket wheel between skids for raking material into a separate suction receiver. An underwater travelling frame for a digging wheel pivotally connected to the lower end of a pushing boom is disclosed in German Pat. No. 2,413,738. A pivotally supported traveling frame for an above surface excavating head is disclosed, on the other hand, in U.S. Pat. No. 3,690,023. In each case, forward travel of the excavating head is effected by towing or pushing.
The underwater dredgers exemplified by the disclosures in the aforementioned prior patents involve relatively large excavating heads at the lower end of the boom which gravitationally exert the requisite digging pressure and require cable-winch systems for lowering and raising the boom under the massive load of the excavating head. Geared power connections to the excavating head are provided from a power source located on the floating vessel in order to rotate the excavating drum during an excavating operation. The propelling force is derived solely from the floating vessel either towing or pushing the excavating drum causing the excavating head to swing in an arc about a spud anchored to the bottom.
It is therefore an important object of the present invention to provide an underwater dredger which will fill an existing void between massive harbor units as aforementioned and very small portable dredgers.
A further object in accordance with the foregoing object is to provide a highly mobile and functionally flexible dredger capable of performing large and small dredging projects. Yet another object is to provide a dredger arrangement which will facilitate maintenance and repair work on the apparatus.